Method for forming cushions

ABSTRACT

A method for forming cushions including the following four steps: (1) a compression step in which the structure ( 2 ) is compressed in a mold ( 3 ); (2) a thermal softening step in which the structure ( 2 ) is thermally softened by means of a heating medium; (3) a curing step in which the structure ( 2 ) directly undergoes forced cooling in a cooling medium, and is then cured; and (4) a mold release step in which the structure ( 2 ) is released from the mold ( 3 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/627,147 filed on Sep. 26, 2012, now pending, which is acontinuation-in-part of International Patent Application No.PCT/JP2011/004921 with an international filing date of Sep. 1, 2011,designating the United States, now pending, and further claims prioritybenefits to Japanese Patent Application No. 2010-196042 filed Sep. 1,2010. The contents of all of the aforementioned applications, includingany intervening amendments thereto, are incorporated herein byreference. Inquiries from the public to applicants or assigneesconcerning this document or the related applications should be directedto: Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 14781Memorial Drive, Suite 1319, Houston, Tex. 77079.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of forming a cushion and especially toa method of secondary formation of a three-dimensional netted structurehaving undergone a primary formation.

More specifically, the invention is directed to a method for forming acushion having excellent impact resistance and load bearing properties,which meets the specific needs of a large number of people in variousfields. Various shapes and sizes of cushions are formed by the method.The method is applicable to seat cushions used for seating, lying, orriding, including in health appliances, and vehicle seats of, e.g.,automobiles, motorbikes, bicycles, trains, ships and boats and aircraft,saddles for horse-riding, chairs, sofas and beds.

2. Description of the Related Art

Japanese Pat. No. 4350286 describes a conventional four-face formingmethod for forming a three-dimensional netted structure, wherein moltenfilaments made of a thermoplastic resin are extruded as the material oras the main material from a die with a nozzle end having a plurality ofnozzle openings so as to naturally fall between partly submerged drawingmachines. The drawing speed of the filaments is set to be lower than thefalling speed. Two pairs of the drawing machines, wherein the drawingmachines of each pair are placed to face each other, are arranged in aquadrilateral formation in the direction perpendicular to the extrudingdirection. The interval between the opposed drawing machines is set tobe narrower than the width of the extruded filament assembly. All fourfaces of the outer periphery of the filament assembly are brought intocontact with the drawing machines before and after the submergedportions of the drawing machines. The density of all the four faces ofthe outer periphery in a direction parallel to the extruding directionis made to be higher than the density of the other part excluding thefour faces. This feature ensures that a post finishing step is notrequired and enhances the alignment.

Japanese Pat. Appl. No. 2003-2510898 proposes a method of forming acushion wherein a three-dimensional structure is placed in a femalemold. The three-dimensional structure is made from solid and/or hollowcontinuous filaments and/or short filaments with random loops or curlsmade of at least a thermoplastic resin and brought into contact with oneanother to be tangled with voids at a specific bulk density. The femalemold and/or the three-dimensional structure are heated to a specifictemperature required for thermally softening the three-dimensionalstructure. The female mold is mated with a male mold with thethree-dimensional structure inbetween and clamped down. Thethree-dimensional structure is allowed to cool down and cure. Thecushion is formed to have a volume corresponding to the stroke of themale mold mating with the deep-drawing female mold.

The method described in Japanese Pat. Appl. No. 2003-2510898 is easierthan secondary processing of urethane foam and meets the more specificneeds than the secondary processing of urethane foam. The compressionmolding method enables formation of any original shape conforming to theindividual build, thus providing high-value-added products. Thethickness of the cushion is controllable with only one mold. This cansatisfy the diverse requirements for the characteristics of variousproducts without providing a wide variety of molds. For example, thelonger stroke produces the thinner cushion, while the shorter strokeproduces the thicker cushion. This facilitates production of the cushionand meets diverse requirements for the characteristics of variousproducts, such as custom-made cushions. Additionally, the spring-likecharacteristics may be controlled freely by changing the diameter, thematerial, the denier, the bulk density or the porosity of the filamentsof the three-dimensional structure. While the spring characteristics ofthe material are unchanged, squeezing by compression molding changes thecushioning effect and varies the load distribution.

The method described in Japanese Pat. No. 4350286, however, requirespost-processing by secondary formation according to the requirements ofthe materials to be produced, for example, to make the rounded edge orto form a recess for chairs. Such secondary formation is requiredespecially for the flame-retardant seat cushion for aircraft to form arecess and make the rounded or flat edge corners. Such secondaryformation is extremely complicated and troublesome. On the other hand,in the method described Japanese Pat. Appl. No. 2003-2510898 thethree-dimensional netted structure is heated and thermally softened, themold is closed for compression molding, and then cooled down, e.g., withwater, to cure the three-dimensional netted structure, and, thereafter,the three-dimensional netted structure is removed from the mold. Themold is large and thereby needs a significantly long time to repeat theheating and the cooling steps. The three-dimensional netted structurecannot be removed from the mold until the temperature of the mold issufficiently low. This increases production time and lowers productionefficiency.

BRIEF SUMMARY OF THE INVENTION

In order to solve at least part of the above-described problems, oneobject of the invention is to shorten the mold release time forreleasing the three-dimensional netted structure from the mold.Shortening the mold release time can improve production efficiency.

In order to achieve the foregoing advantages, the three-dimensionalnetted structure is directly heated to enhance the efficiency, insteadof heating the mold as described in Japanese Pat. Appl. No.2003-2510898. Additional embodiment of the invention are describedhereinbelow.

DEFINITIONS

The “heating medium” may, for example, be steam, hot blast or hot water.The “coolant” may be liquid or cold air.

The “three-dimensional netted structure” may be a netted structure madefrom a plurality of continuous filaments respectively formed in randomloops and brought into contact with one another to be tangled with voidsat a specified bulk density. The “continuous filaments” are tangled atrandom in loops by extrusion and are made to partly adhere to oneanother with heat, so as to form the spring-like structure.

The “three-dimensional netted structure” may be made of a thermoplasticresin as the material, for example, polyolefin resin such aspolyethylene (PE) or polypropylene (PP), polyester such as polyethyleneterephthalate, polyamide such as nylon 66, vinyl chloride resin such aspolyvinyl chloride, or styrene resin such as polystyrene.

The polyethylene (PE) may be low-density polyethylene (LDPE), linearlow-density polyethylene (LLDPE), very-low-density polyethylene (VLDPE),high-density polyethylene (HDPE), or ethylene-vinyl acetate copolymerresin (EVA).

The material may otherwise be a copolymer copolymerized with any of theabove resins as the base, an elastomer or a resin mixture containing anyof the above resins, or may be a recycled material or a material mixturecontaining a flame retardant, a non-flammable material and/or anantimicrobial agent.

The material may be a mixture of the “thermoplastic resin” with vinylacetate resin (hereinafter referred to as VAC), ethylene-vinyl acetatecopolymer (hereinafter referred to as EVA) or styrene butadiene styrene(hereinafter referred to as SBS), etc. For example, the material may bea mixture of a polyolefin resin with vinyl acetate resin, ethylene-vinylacetate copolymer or styrene butadiene styrene. The material may be amixture (for example, thermoplastic elastomer) of the polyolefin resinsuch as PE or PP and VAC, EVA or SBS.

The mixing ratio of the polyolefin resin to the vinyl acetate content ofVAC or EVA is 70 through 97 percent by weight to 30 through 3 percent byweight or preferably 80 through 90 percent by weight to 20 through 10percent by weight. The VAC or EVA content of not greater than 3 percentby weight may cause the low impact resistance, while the content of notless than 30 percent by weight may cause the poor thermal properties.The mixing ratio of the polyolefin resin to SBS is 50 through 97 percentby weight to 50 through 3 percent by weight or more preferably 70through 90 percent by weight to 30 through 10 percent by weight. Thepolyolefin resin may be recycled resin.

The “continuous filaments” may be solid or hollow. In the hollowcontinuous filaments, the air is trapped in the tubular structure of thefilaments. This advantageously provides the characteristics of the airspring and thereby the specific cushioning effect and also preventsbuckling. Inclusion of the air keeps the rigidity of thethree-dimensional structure. The hollow may be continuous or discrete.One filament may include a hollow section and a solid section. Themixing ratio of the solid filaments to the hollow filaments ispreferably 10 through 80 to 90 through 20. The arrangement of locatingthe hollow filaments in the center area and placing the solid filamentsto surround the periphery of the hollow filaments advantageously givesgood touch.

The diameter of the solid “continuous filaments” is preferably 0.3 to3.0 mm or more preferably 0.5 to 1.0 mm. The solid filaments having thediameter of not greater than 0.3 mm have the low tenacity, whichincreases the adhesion area and thereby decreases the porosity. Thesolid filaments having the diameter of not less than 3.0 mm have theexcessive tenacity, which prevents formation of loops or curls todecrease the adhesion area and thereby decrease the strength. Thediameter of the hollow “continuous filaments” is preferably 0.6 to 3.0mm or more preferably 0.9 to 1.5 mm. The void rate of not higher than10% does not have contribution to weight reduction.

The bulk density of the “three-dimensional netted structure” is 0.03 to0.20 g/cm³ or preferably 0.05 to 0.15 g/cm³. The bulk density of nothigher than 0.03 g/cm³ decreases the strength, while the bulk density ofnot lower than 0.11 g/cm³ does not substantially reduce the weight andeliminates the elasticity. The “three-dimensional netted structure” maynot have a uniform density as the whole but may have a varying-densitystructure at predetermined intervals or at adequate intervals. In thisstructure, the bulk density in the coarse part is 0.03 to 0.13 g/cm³,preferably 0.04 to 0.11 g/cm³ or more preferably 0.05 to 0.09 g/cm³. Thebulk density in the dense part is 0.04 to 0.20 g/cm³, preferably 0.05 to0.15 g/cm3 or more preferably 0.06 to 0.13 g/cm³.

The three-dimensional netted structure of varying density may becompressed with a mold to have a lower density at an area where awrinkle may occur. This results in a formed product without anywrinkles.

The porosity of the “three-dimensional netted structure” is 80 to 98%,preferably 90 to 97% or more preferably 91 to 96%. The porosity of thisrange is preferable to maintain the elasticity and the strength as thecushion and reduce the weight:

[Porosity (%)]=(1−[bulk density]/[resin density])×100%

The method of forming the cushion is applicable to form the “cushion”used for seating, lying or riding, for example, any of healthappliances, vehicle seats of, e.g., automobiles, motorbikes, bicycles,trains and aircraft, saddles for horse-riding, chairs, sofas and beds.This method is especially preferable to form the vehicle seat cushionof, for example, aircraft, rockets, trains, ships and boats, andsubmarines.

The applicable range of this method is not limited to these examples,but the method is widely applicable to form the cushion used forseating, lying or riding with or without vibration, as the alternativeof the conventional urethane foam seat cushion.

The “mold” is preferably made of metal, plastic, or concrete.

The structure may be cooled down by natural cooling or by forciblecooling (by the air or water).

Advantages of the Invention

The method of forming the cushion described herein shortens the moldrelease time of releasing the three-dimensional netted structure fromthe mode, thus improving the production efficiency.

In certain embodiments of the method, the compression step is performedprior to the thermal softening step. This may reduce the amount ofheating required for softening.

In certain embodiments of the method, the thermal softening step isperformed prior to the compression step. This enables even a materialrequiring a relatively long softening time to be adequately treated.

In certain embodiments of the method, the compression step and thethermal softening step are performed simultaneously. This shortens theworking time.

In certain embodiments of the method, the mold has an opening, so that aheat medium or a coolant can be supplied through the opening. Thisenables size reduction.

In certain embodiments of the method, the method includes an additionalcompression step of additionally compression-forming a compressed partof the three-dimensional netted structure, wherein an end area of theadditionally compression-formed part is formed to a fastening rim forfastening the three-dimensional netted structure to another object. Thisdoes not require production of a separate fastener, thus improving theworking efficiency and reducing the cost.

In certain embodiments of the method, the end area has a lower densitythan the density of another area. This produces a product having a lessvariation in density.

In certain embodiments of the method, the method further includes asurface treatment step or an adhesive spray step. This is convenient forantistatic treatment or flame-retardant treatment.

In certain embodiments of the method, the method further includes anadhesion step of bonding cloth to the three-dimensional nettedstructure. This is suitable to manufacture, for example, seats.

In certain embodiments of the method, the method is performed incombination with a method of processing the formed three-dimensionalnetted structure by hot press, high-frequency wave, or ultrasonic wave.The formed object is accordingly subjected to secondary formation byfurther heating, further depression, adhesion or fusion to form adesired shape and provide an additional function.

In certain embodiments of the method, the thermal softening stepthermally softens the three-dimensional netted structure by hot press,by high-frequency heating or by ultrasonic wave. This advantageouslyshortens the process time.

In certain embodiments of the method, the thermal softening stepincludes a pre-heating step and a main thermal softening step. Thisadvantageously shortens the process time.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to accompanyingdrawings, in which:

FIG. 1 shows a block diagram illustrating a process flow of an exemplaryembodiment according to the method of forming a cushion of theinvention;

FIG. 2 shows a block diagram illustrating a process flow of anotherembodiment according to the method of forming a cushion of theinvention;

FIG. 3 shows a block diagram illustrating a process flow of yet anotherembodiment according to the method of forming a cushion of theinvention;

FIG. 4 illustrates a process flow of an exemplary embodimentcorresponding to the block diagrams in FIGS. 1-3;

FIG. 5 illustrates another process flow of an exemplary embodimentcorresponding to the block diagrams in FIGS. 1-3;

FIG. 6( a) is a partial cross-sectional front view illustrating anexemplary mold;

FIG. 6( b) is a partial cross-sectional front view illustrating anotherexemplary mold;

FIGS. 7( a) and 7(b) illustrate a step of end-face processing accordingto another embodiment of the invention;

FIGS. 8( a) to 8(c) illustrate a step of end-face processing accordingto a further embodiment of the invention;

FIG. 9 shows the formed surface of a three-dimensional netted structureaccording to an exemplary embodiment;

FIG. 10 is an enlarged image view of FIG. 9;

FIG. 11 shows the end face of the three-dimensional netted structureaccording to an exemplary embodiment;

FIG. 12 is a perspective surface side view showing a formed objectaccording to an embodiment of the invention;

FIG. 13 is a perspective rear face view showing a formed objectaccording to an embodiment of the invention;

FIG. 14 illustrates a three-dimensional netted structure that requiresprocessing;

FIG. 15( a) is a partial cross-sectional front view illustrating athermal softening step according to an exemplary embodiment of theinvention;

FIG. 15( b) is a partial cross-sectional front view illustrating athermal softening step according to another exemplary embodiment of theinvention;

FIG. 16( a) is a partial cross-sectional front view illustrating athermal softening step according to yet another exemplary embodiment ofthe invention;

FIG. 16( b) is a plan view illustrating the thermal softening step shownin FIG. 16( a);

FIG. 17 is a plan view illustrating a thermal softening step accordingto yet another exemplary embodiment of the invention;

FIG. 18 is a partial cross-sectional front view illustrating the thermalsoftening step shown in FIG. 17;

FIG. 19 is a planar image view showing the material of thethree-dimensional netted structure according to an exemplary embodimentof the invention;

FIG. 20 is a planar image view showing the formed surface of a cushionaccording to another exemplary embodiment of the invention; and

FIG. 21 is a planar image view showing the formed surface of a cushionaccording to an exemplary embodiment.

In FIGS. 4 to. 8 and 15 to 18, the random curled texture of thethree-dimensional netted structure of the seat cushion has been omittedfrom the illustration and only its contour line is shown.

DETAILED DESCRIPTION OF THE INVENTION

The following describes the method of forming a seat cushion fromcontinuous filaments tangled at random in loops and made to partlyadhere to one another with heat according to certain embodiments of theinvention, with reference to the accompanied drawings.

The seat cushion 1 (hereinafter referred to as “cushion 1”) is made froma three-dimensional structure 2 (hereinafter referred to as “structure2”) made of a material that may be a mixture (e.g., thermoplasticelastomer) of a thermoplastic resin, e.g., polyolefin resin, such as PEor PP and VAC, EVA, or SBS.

Three or four of the four surfaces of the structure 2, with theexception of its two end faces relative to the extruding direction, areformed during the curing step and generally have a higher density thanthat of the other area. The structure 2 is formed in a rectangular prismhaving a total of six faces including the top face, bottom face, leftside face and right side face (see FIGS. 9 and 10) and two cut end faces(see FIG. 11). The details of the structure 2 will be described below.

The forming method of the embodiment is performed for, for example,recess formation and end-face processing, as shown in FIG. 14. Therecess formation may form a recess conforming to, for example, the shapeof the legs, the shape of the back or the shape of the buttock. Therecess may be formed by pressing a target area of the structure with amold and exposing the structure to steam. The end-face processing maypress the end faces of the structure 2 to form thinner-walled areas.

The method according to a first embodiment has the following steps:

-   -   (1) compression step of compressing the structure 2 with a mold        3;    -   (2) thermal softening step of thermally softening the structure        2 with a heating medium;    -   (3) curing step of directly and forcibly cooling down the        structure 2 with a coolant to cure the texture; and    -   (4) mold release step of releasing the structure 2 from the mold        3.

In step (1), the structure 2 is compressed to be deformed with the mold3 and kept in the compressed state for a predetermined time as shown inFIGS. 4( a) and 5(a).

The mold 3 has the shape conforming to a target form. For example, themold 3 may have a downward curved shape, e.g., a dish shape, to form thecurved convex part. This forms the partial area of the structure 2 to acurved shape (for example, R shape). The mold 3 may be provided with orwithout holes. In the former case, the number of holes may be selectedarbitrarily according to the forming conditions, and the arrangement ofthe holes may be set adequately. One preferable example of the mold 3 isa dish-shaped punching metal member 3 with openings 4 shown in FIG. 6(a). Another preferable example of the mold 3 is a dish-shaped mesh metalmember 3 shown in FIG. 6( b). The mesh metal member 3 includes a mesh30, meshed openings 4 and a circular edge member 5 provided on thecircumferential end to have the larger diameter than that of the mesh30. The mechanical force of a pressing machine may be applied forcompression.

In step (2), the structure 2 is softened with supply of heat. Heatingthe structure 2 with the heating medium may spray steam, blow hot blastor spray hot water. The forming method of this embodiment requires atemperature of or above the thermal softening temperature of thematerial resin of the filaments in the structure 2. The heatingtemperature of the structure 2 is preferably not higher than 100 degreesCelsius. The cushion 1 may, however, be formed at the temperature above100 degrees Celsius by taking into account the melt temperature of theresin, such as heat-resistant resin. The temperature range of theheating medium may be set to include a wide range of low temperature tohigh temperature by taking into account the forming conditions, and maybe, for example, 40 to 200° C. The direct supply of the heating mediumto the structure 2 may directly supply the steam to the voids of thethree-dimensional netted structure.

The mold 3 is required to have some hole or inlet, and it is preferableto use the openings 4 as shown in FIG. 6 for this purpose. The mold 3may be a mesh metal member. The excessively large mesh of the mesh metalmember may leave the trace of the mesh shape, and the adequate-size meshis preferable. In the examples of FIG. 6, steam is supplied from a steamnozzle 6 through the openings 4 onto the structure 2. The outlettemperature of the steam nozzle 6 is preferably 90 to 100° C.

Supplying the steam, hot water, or hot blast onto the structure 2compressed with the mold 3 thermally soften the structure 2. Applyinghot water of or approximate to 100° C. may melt and recess the hotwater-applied part of the structure 2 made of some resin. Adequateheating is thus required, for example, by applying hot water little bylittle or by taking into account the temperature conditions.

In step (3), water is applied onto the structure 2 and the mold 3 tocool down and cure the structure 2. For example, water or cold water maybe applied onto the structure 2 and the mold 3 from a cooling source(not shown). This forcibly supplies the coolant through the openings 4onto the structure 2 to forcibly cool down and cure the structure 2.

In step (4), the mold 3 is released from the structure 2. This enablesthe series of operations including the mold release step to be repeatedat extremely short time intervals and thus ensures the good workability.

The method according to a second embodiment has the following steps:

-   -   (1) thermal softening step of thermally softening the structure        2 with a heating medium;    -   (2) compression step of compressing the structure 2 with a mold        3;    -   (3) curing step of directly and forcibly cooling down the        structure 2 with a coolant to cure the texture; and    -   (4) mold release step of releasing the structure 2 from the mold        3.

The method of the second embodiment performs the thermal softening stepand the compression step in the reverse order to that of the firstembodiment.

The method according to a third embodiment has the following steps:

-   -   (1) thermal softening/compression step of thermally softening        the structure 2 with a heating medium, while compressing the        structure 2 with a mold 3;    -   (2) curing step of directly and forcibly cooling down the        structure 2 with a coolant to cure the texture; and    -   (3) mold release step of releasing the structure 2 from the mold        3.

The method of the third embodiment simultaneously performs the thermalsoftening step and the compression step of the first embodiment or thesecond embodiment.

The softening step enables the three-dimensional structure of thevarying density to be formed homogeneously. This allows the seat cushionto have the hard ends and advantageously improves the durability of theseat cushion.

According to the first to the third embodiments, the mold 3 may bepreferably made of a metal plate, a resin plate or a cement plate withopenings, and the heating medium may be supplied preferably through theopenings 4. It is preferable that the mold 3 has the smaller surfacearea than the surface area of the structure 2.

According to the first to the third embodiments, the method may furtherinclude an additional compression step of additionallycompression-forming the compressed part of the structure to form an endarea of the structure to a fastening rim for fastening the structure toanother object.

According to the first to the third embodiments, the method may furtherinclude an end compression step as the additional step to form an endarea of the structure to a fastening rim for fastening the structure toanother object. In the illustrated example of a chair cushion, a rim 7is formed in the peripheral area surrounding a center convex 16 as shownin FIG. 8( a). The rim 7 is folded down to the rear face of the base ofa chair 8 as shown in FIG. 8( b) and is secured to the base withattachments 9. The attachment may be a fastener such as rivet or screwor may be a drive clamp (U-shaped needle). The drive clamps are drivenfrom the rear face of the rim to fasten the structure 2 to the chair. Asurface layer material, such as artificial leather may be attachedsimultaneously or may be sewn in a later step. Formation of the rim 7requires higher-temperature heating with, for example, ultrasonic waveor a heater.

According to the first to the third embodiments, an end area 2 a is madeto have the lower density than another area 2 b as shown in FIG. 7. Thisis because the high density may cause failure in adequately compressingthe end area. The end area 2 a is easily compressed to crush its textureand thereby have the optimum density. The end area of the lower densityis readily crushable, and there is a less variation in density betweenthe end area and another area after the crush. According to anotherembodiment, the end area 2 a may have the high density to beintentionally hardened.

According to the first to the third embodiments, the additional step maybe a surface treatment step or an adhesive spray step after the moldrelease step. The surface treatment may be, for example, flame-retardanttreatment or antistatic treatment. The adhesive may be used to bond anadditional material, such as a surface material or a decorativematerial.

According to the first to the third embodiments, the additional step maybe an adhesion step of bonding the cloth to the structure 2 after themold release step.

In one application, a lighting apparatus may be placed behind thecushion for backlighting.

Method of Forming Structure 2

The following describes the structure 2. Refer to Japanese Pat. No.4350286 or Japanese Pat. Appl. No. 2003-2510898 for the details. Thestructure 2 of the embodiment is provided as a three-dimensionalstructure with voids made from continuous filaments of the mixturematerial tangled at random in a plurality of loops. The filaments may besolid or hollow.

The bulk density of the three-dimensional structure is 0.03 to 0.20g/cm³, preferably 0.05 to 0.15 g/cm³ or more preferably 0.06 to 0.13g/cm³. The porosity of the three-dimensional structure is 80 to 98%,preferably 90 to 97% or more preferably 91 to 96%.

The method of forming the structure 2 according to the embodiment maydry-blend the material mixture of the polyolefin resin, such as PE orPP, and the additional component VAC, EVA or SBS as needed basis with atumbler, a cut feeder or a volumetric feeder or may mix or melt-mix andpelletize the material mixture to pellets and may feed the dry-blendedmaterial mixture or the pellets to a hopper of an extruder.

More specifically, the material mixture of, for example, PP and SBS, ismixed at 40 rpm for 15 minutes with a tumbler (KR mixer manufactured byKATO-RIKI MFG. CO., LTD.)

The material mixture is loaded in a hopper of a 90 mφ single screwextruder, is melt-kneaded at a specified temperature (for example, 200to 260° C.), is melt-extruded at a specified extrusion rate from a largenumber of nozzles of a specified diameter provided in a molding die, andis drawn with a drawing machine to form solid and/or hollow filaments ofa specified diameter (for example, 600 to 90,000 deniers, preferably3,000 to 30,000 deniers or more preferably 6,000 to 10,000 deniers). Thefilaments in the molten state are formed to loops of 1 to 10 mm indiameter or preferably 1 to 5 mm in diameter, and the adjacent filamentsare brought into contact with one another and are tangled in a bath (inwater) to form random loops. The moving rate of a roll or a belt of thedrawing machine is set to be lower than the extrusion rate. The upperpart of the drawing machine is protruded above the water surface, andthe remaining part of the drawing machine is submerged in water. Thecontinuous filaments are drawn with this drawing machine. During thedrawing process, the continuous filaments are formed to random loops,and the adjacent loops are partly tangled and are brought into contactwith one another to adhere to one another. The continuous filaments aresolidified in water and are wound on a wind roll to form a filamentassembly (for example, 10 to 200 mm in thickness and 2,000 mm in width).It is preferable that at least part of the tangled contact areasmelt-adhere to one another. The filaments may be a mixture of hollowfilaments and solid filaments at a specified ratio.

The wound filament assembly is cut into an adequate length with a cutterto the structure 2.

While the filaments formed in loops in water are drawn with the drawingmachine, the cushioning properties may be changed by varying the speedof the drawing machine. The bulk density of the three-dimensionalstructure may be relatively increased to 0.04 to 0.20 g/cm³, preferably0.05 to 0.15 g/cm³ or more preferably 0.06 to 0.13 g/cm³. The porosityof the three-dimensional structure may be decreased to 80 to 98%,preferably 90 to 97% or more preferably 91 to 96%.

According to one embodiment, before the continuous filaments are broughtinto contact with the water surface of a water tank, a specific part ofthe continuous filaments expected to form the peripheral side faces ofthe resulting filament assembly may be squeezed with the drawing machineto have the increased bulk density. This gives the structure 2 havingthe surface layer of the higher density. According to anotherembodiment, before the continuous filaments are brought into contactwith an endless belt of a conveyer or a draw roll, the surface of thecontinuous filaments may be cooled and solidified. This protects theresulting product from the bite of the belt. The loops are preferablyformed to have the smooth surface, in order to allow uniform adhesion ofthe loops.

While the continuous filaments formed to loops in water are drawn withthe drawing machine, the speed of the drawing machine may be varied tochange the properties of the three-dimensional netted structure. Thedrawing speed of the drawing machine may be regulated to decrease atspecified intervals (for example, 3 to 5 m). For example, the drawingspeed of the draw roll may be set to be lowered for a predetermined timeperiod at specified time intervals, for example, with a timer. This mayform the three-dimensional netted structure of the varying densityincluding the portions of the higher bulk density formed by thelower-speed drawing at specified intervals (for example, 30 to 50 cm)and the other portions along the longitudinal direction of thethree-dimensional netted structure.

The structure 2 formed by the above forming method has, for example, thebulk density of 0.07 g/cm³ and the thickness of 50 mm. Thethree-dimensional structure may be formed to have one single set ofproperties or may be formed to have multiple different sets ofproperties. Refer to the descriptions of Japanese Pat. No. 4350286 andJapanese Pat. Appl. No. 2003-2510898 for the details includingproduction examples of the structure 2 formed by the above formingmethod and results of their experiments.

As described above, the method of forming the cushion according to theinvention is preferably applied to form a seat cushion used for seating,lying or riding with or without vibrations, as the alternative of theconventional urethane foam seat cushion, for example, any of vehicleseats of, e.g., automobiles, motorbikes, bicycles, trains and aircraft,saddles for horse-riding, chairs, sofas and beds.

The method of forming the cushion of the invention is not limited to theabove embodiments but may be applied to various other embodiments withinthe scope of the invention. There may be various modifications andvariations made to the embodiments without departing from the scope ofthe invention. These modification, variations, and equivalents are alsoincluded in the scope of the invention.

The structure 2 may have the dimensions of 100 mm to 300 mm in length,100 mm to 300 mm in width and 30 mm to 150 mm in thickness but is notlimited to such dimensions. The structure 2 may be formed to have anyarbitrary size depending on its applications for, e.g., infants, elderlypeople or adults by, for example, melt-cutting, mechanical cutting orhot press.

The forming methods according to fourth and fifth embodiments employ hotpress for the thermal softening step described in the first to the thirdembodiments, as shown in FIGS. 15( a) and 15(b). The structure 2 isplaced between a heated upper mold 3 a and a heated lower mold 3 b, ispartially compressed to be crushed, and is kept in the compressed state.The structure 2 is then released from the upper mold 3 a and the lowermold 3 b. In some heating temperature condition, the compressed part ofthe structure 2 may be molten to a sheet. The upper mold 3 a and thelower mold 3 b are preferably metal molds. There is no space between theupper surface of the structure 2 and the upper mold 3 a in the state ofFIG. 15( a), while a space 10 is formed in the state of FIG. 15( b). Inthe high heating temperature condition, the upper surface of thestructure 2 may be depressed by the heat of the upper mold 3 a in thestate of FIG. 15( a). The presence of the space 10 advantageouslyprevents such depression. The upper mold 3 a is attached to an upperplate 11, while the lower mold 3 b is attached to a lower plate 12. Inthe forming methods of the first to the third embodiments, supplying hotwater may cause depression of the structure, while steam may notsufficiently heat the inside of the structure 2. The forming methodsaccording to the fourth to seventh embodiments employ hot press, inorder to solve such problems.

The forming method according to a sixth embodiment uses the upper mold 3a of the frame structure with compression elements to form the space 10as shown in FIGS. 16( a) and 16(b). The frame structure of the mold 3 aaims to decrease the weight of the upper mold 3 a and prevent depressionon the upper surface of the structure 2, which may occur in sometemperature and other manufacturing conditions. The upper plate 11 isomitted from the illustration of FIG. 16( a). Support columns 13 havethe lower ends fastened to the upper mold 3 a and the upper endsfastened to the upper plate 11.

The forming method according to a seventh embodiment additionally formsa middle compressed part to the structure of the sixth embodiment asshown in FIGS. 17 and 18. The three-dimensional netted structure 2 hasthe middle compressed part, in addition to the peripheral compressedparts. For this purpose, the upper mold 3 a has the frame structure witha partition plate 3 c provided in the middle of the inner area of theupper mold 3 a and connected on both ends.

In the forming methods of the fourth to the seventh embodiments, thethermal softening step preferably includes a pre-heating step and a mainhot press step. The presence or the absence of pre-heating varies thecurvature of the rising shape in the compressed part of the structure 2.Pre-heating increases the curvature. The pre-heating step preferablyuses a hot blast tank (the temperature is preferably 70 to 95° C. butmay be 95 to 220° C. according to the material and the pre-heatingmode). Hot water may be used for pre-heating, but an additional dryingstep is needed. When PE is used for the material, the pre-heatingtemperature is preferably 70 to 95° C. and the pre-heating time ispreferably 5 to 30 minutes, and the hot press temperature is preferably110 to 130° C. When polyester elastomer is used for the material, thepre-heating temperature is preferably 80 to 120° C. and the pre-heatingtime is preferably 1 to 30 minutes, and the hot press temperature ispreferably 230 to 280° C. The temperature range and the time range maybe adjusted according to the resin used and the mold structure. In orderto form a certain shape, the pre-heating step and the main hot pressstep may be performed repeatedly.

In application of ultrasonic wave or high-frequency wave for heating, anultrasonic heater or a high-frequency generator may be used without theupper mold 3 a and the lower mold 3 b.

The invention is not limited to the above embodiments but variousmodifications and variations may be made to the embodiments withoutdeparting from the scope of the invention. Such modifications andvariations, as well as their equivalents are also included in the scopeof the invention.

INDUSTRIAL APPLICABILITY

The invention is mainly applicable to secondary forming, such asend-face processing and recess formation, of the three-dimensionalnetted structure.

The embodiments and their examples discussed above are to be consideredin all aspects as illustrative and not restrictive. There may be manymodifications, changes, and alterations without departing from the scopeor spirit of the main characteristics of the present invention. Allchanges within the meaning and range of equivalency of the claims aretherefore intended to be embraced therein. The scope and spirit of thepresent invention are indicated by the appended claims, rather than bythe foregoing description.

All publications and patent applications mentioned in this specificationare indicative of the level of skill of those skilled in the art towhich this invention pertains. All publications and patent applicationsmentioned in this specification are herein incorporated by reference tothe same extent as if each individual publication or patent applicationmentioned in this specification was specifically and individuallyindicated to be incorporated by reference.

REFERENCE CHARACTER LIST

-   -   1. Cushion    -   2. Three-dimensional netted structure    -   2 a. End area    -   2 b. Another area    -   3. Mold    -   4. Openings    -   5. Edge member    -   6. Steam nozzle    -   7. Rim    -   8. Chair    -   9. Attachment    -   3 a. Upper Mold    -   3 b. Lower Mold    -   10. Space    -   11. Upper Plate    -   12. Lower Plate    -   13. Support Column    -   16. Convex

What is claimed is:
 1. A method of forming a cushion having a spring-like structure made of continuous filaments tangled at random in loops and made to partly adhere to one another with heat, the method comprising: a compression step of compressing a three-dimensional netted structure having two surfaces, three surfaces, four surfaces, or a greater number of surfaces formed thereon with a mold; a thermal softening step of thermally softening the three-dimensional netted structure with a heating medium; a curing step of forcibly or naturally cooling down the three-dimensional netted structure with a coolant to cure texture of the three-dimensional netted structure; and a mold release step of releasing the three-dimensional netted structure from the mold; wherein: an area of the three-dimensional netted structure which is to be compressed in the compressing step has a lower density than other areas of the three-dimensional netted structure.
 2. A method of forming a cushion having a spring-like structure made of continuous filaments tangled at random in loops and made to partly adhere to one another with heat, the method comprising: a thermal softening step of thermally softening a three-dimensional netted structure having two surfaces, three surfaces, four surfaces, or a greater number of surfaces formed thereon with a heating medium; a compression step of compressing the three-dimensional netted structure with a mold; a curing step of forcibly or naturally cooling down the three-dimensional netted structure with a coolant to cure texture of the three-dimensional netted structure; and a mold release step of releasing the three-dimensional netted structure from the mold; wherein: an area of the three-dimensional netted structure which is to be compressed in the compressing step has a lower density than other areas of the three-dimensional netted structure.
 3. The method of claim 1, wherein the compression step and the thermal softening step are performed simultaneously.
 4. The method of claim 2, wherein the compression step and the thermal softening step are performed simultaneously.
 5. The method of claim 1, wherein the thermal softening step thermally softens the three-dimensional netted structure by hot press instead of by using the heating medium.
 6. The method of claim 2, wherein the thermal softening step thermally softens the three-dimensional netted structure by hot press instead of by using the heating medium.
 7. The method of claim 5, wherein the thermal softening step includes a pre-heating step for pre-heating the three-dimensional netted structure and a main thermal softening step.
 8. The method of claim 6, wherein the thermal softening step includes a pre-heating step for pre-heating the three-dimensional netted structure and a main thermal softening step.
 9. A method of forming a cushion having a spring-like structure made of continuous filaments tangled at random in loops and made to partly adhere to one another with heat, the method comprising: a compression step of compressing a three-dimensional netted structure having two surfaces, three surfaces, four surfaces, or a greater number of surfaces formed thereon with a mold; a thermal softening step of thermally softening the three-dimensional netted structure with a heating medium; a curing step of forcibly or naturally cooling down the three-dimensional netted structure with a coolant to cure texture of the three-dimensional netted structure; and a mold release step of releasing the three-dimensional netted structure from the mold; wherein: the mold has a smaller surface area than a surface area of the three-dimensional netted structure.
 10. A method of forming a cushion having a spring-like structure made of continuous filaments tangled at random in loops and made to partly adhere to one another with heat, the method comprising: a thermal softening step of thermally softening a three-dimensional netted structure having two surfaces, three surfaces, four surfaces, or a greater number of surfaces formed thereon with a heating medium; a compression step of compressing the three-dimensional netted structure with a mold; a curing step of forcibly or naturally cooling down the three-dimensional netted structure with a coolant to cure texture of the three-dimensional netted structure; and a mold release step of releasing the three-dimensional netted structure from the mold; wherein: the mold has a smaller surface area than a surface area of the three-dimensional netted structure.
 11. The method of claim 9, wherein the compression step and the thermal softening step are performed simultaneously.
 12. The method of claim 10, wherein the compression step and the thermal softening step are performed simultaneously.
 13. The method of claim 9, wherein the mold is a punched metal member having punched holes or a mesh metal member having a mesh, and the heating medium is supplied through the punched holes or the mesh.
 14. The method of claim 10, wherein the mold is a punched metal member having punched holes or a mesh metal member having a mesh, and the heating medium is supplied through the punched holes or the mesh.
 15. The method of claim 9, wherein the thermal softening step thermally softens the three-dimensional netted structure by hot press instead of by using the heating medium.
 16. The method of claim 10, wherein the thermal softening step thermally softens the three-dimensional netted structure by hot press instead of by using the heating medium.
 17. The method of claim 15, wherein the thermal softening step includes a pre-heating step for pre-heating the three-dimensional netted structure and a main thermal softening step.
 18. The method of claim 16, wherein the thermal softening step includes a pre-heating step for pre-heating the three-dimensional netted structure and a main thermal softening step. 